A cognitive 鈥渟peed training鈥� game that cuts dementia risk by 25 per cent alters levels of beta-amyloid, a protein that clogs up the brain in Alzheimer鈥檚 disease, in men, but not in women.

It is the first time brain training has been shown to influence the levels of a neurodegenerative marker, strengthening the evidence suggesting that mental exercises can boost brain health.

鈥淥ne of the main markers that鈥檚 indicative of future dementia risk got better for men who completed cognitive speed training,鈥� says聽聽at Clemson University in South Carolina, who presented the research at the Alzheimer鈥檚 Association International Conference in London on 12 July.

The computer-based speed training involves recalling where objects have flashed up, with the task becoming harder as performance improves. A prior 20-year study by some of Chai鈥檚 colleagues showed that people aged 65 and older, who did the training were聽25 per cent less likely to be diagnosed with Alzheimer鈥檚 disease聽or a related form of dementia compared with a control group.

In the latest study, Chai and her team recruited a separate group of 53 people from the US aged 65 and older, 13 of whom were male. About a third of the participants were asked to complete between 2 and 4 hours of speed training each week for 4.5 months.

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The remaining participants were either told to spend the same amount of time playing games such as Solitaire, word search and a game similar to Connect 4, or to complete another kind of brain training in which they had to strategically track objects and switch between tasks.

To explore how speed training may reduce dementia risk, the team collected blood samples from all of the participants at the start and end of the training period.

This revealed that, among men, speed training increased the ratio of two forms of beta-amyloid found in the blood, which suggests the training boosted the brain鈥檚 ability to clear beta-amyloid 42. This protein forms clumps called plaques in the brain during Alzheimer鈥檚 disease, disrupting brain function. The other two kinds of training had no effect.

鈥淚t鈥檚 a really cool finding,鈥� says聽聽at McGill University in Montreal. 鈥淚t is definitely strengthening what they鈥檝e [previously] shown with the reduction in dementia.鈥�

Some Alzheimer鈥檚 treatments, such as lecanemab, have been designed to help clear amyloid from the brain, but they only marginally slow cognitive decline during Alzheimer鈥檚 disease. The limited benefit seen in trials is probably down to these treatments being taken at a relatively late stage of the condition, when substantial brain damage has already occurred, says at University College London.

Engaging in cognitive training to reduce beta-amyloid build-up before dementia develops may have a bigger effect on dementia because it would be done before much brain damage has occurred, says Castegnaro.

However, cognitive training had no effect on amyloid levels in female participants in the study. This suggests that speed training reduces dementia risk in different ways in women and men, says Chai.

The team hopes to explore how speed training may benefit women in future studies, says Chai. But first, the findings need to be verified in geographically and ethnically diverse groups, says Novozhilova.

Severe cystitis, pneumonia or tooth decay could increase the risk of dementia. A study of hundreds of thousands of people across Finland has found that people who were treated in hospital for these infections were significantly more likely to develop dementia 鈥� including an early-onset form of the condition 鈥� within the next six years.

We increasingly think that dementia, including Alzheimer鈥檚 disease, could be prevented or delayed through brain-training games, steadfast lifestyle changes and even saunas. Now, the latest research adds to the mounting evidence supporting infection avoidance to further reduce the odds of developing the condition. 鈥淚t suggests that dementia risk may be partially modifiable,鈥� says at Emory University in Atlanta, Georgia, who wasn鈥檛 involved in the study.

In 2021, at the University of Helsinki and his colleagues noticed that . But it was unclear whether this was because they had other conditions like diabetes, which increases both the risk of and .

To untangle this, they have now analysed the health records of 62,555 people aged 65 or over who hadn鈥檛 been diagnosed with dementia in 2016, but received such a diagnosis between 2017 and 2020. These people were compared with another 312,772 individuals without dementia, whom the team matched for age, sex, education level and marital status. For all the participants, the researchers tracked any diagnoses and hospitalisations that had occurred over the previous two decades.

The team identified 29 conditions that were associated with at least a 20 per cent higher risk of developing dementia five to six years later, on average. Most of these were non-infectious, such as conditions that affect the heart or brain. But two were infections: cystitis 鈥� a urinary tract infection (UTI) that is usually caused by bacteria 鈥� and bacterial infections without a specifically affected site noted in the records. Further analyses revealed that most of the heightened dementia risk was related to these infections, not the 27 other conditions.

Although inflammation is an important immune response to infections, it is also a critical component of some types of dementia, like Alzheimer鈥檚. Infection-related inflammation could provoke breaches in the circulatory system that affect the brain, causing microscopic bleeds or the infiltration of toxins past the blood-brain barrier, says Sipil盲. Evidence is also mounting that vaccines against infections such as shingles and flu reduce our dementia risk.

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In another part of the study, the researchers focused on early-onset dementia, which occurs before age 65. They found that Parkinson鈥檚 disease and head trauma seemed to raise the risk the most, but multiple infections were also implicated, with gastroenteritis, infectious or unspecified colitis (inflammation of the colon), pneumonia, tooth decay and bacterial infections of unspecified sites all roughly doubling the risk.

It is unclear why some infections are linked to early-onset but not regular-onset dementia, and vice versa, but the researchers note in their paper that the causes and genetic susceptibility associated with these forms of the condition vary.

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Despite these strong associations, we don鈥檛 know whether these infections actually cause dementia, or if the team has just observed correlations, despite attempting to adjust for those, says Sipil盲. 鈥淚deally, intervention trials should examine whether better infection prevention helps reduce dementia occurrence or delay the onset of this disease,鈥� he says.

at University College London says she wouldn鈥檛 be surprised if such research confirmed a cause-and-effect relationship. 鈥淭his high-quality study, in line with other evidence, the timeline and the biological plausibility make it more likely,鈥� she says.

This could inspire better prevention, management and monitoring of severe infections, says Wu. For cystitis, for example, prevention can include ensuring adequate hydration and good incontinence care. 鈥淥n the management side, prompt treatment is particularly important because UTIs in older adults often present atypically 鈥� such as confusion or delirium rather than the classic symptoms 鈥� meaning they can be missed or treated too late,鈥� she says. 鈥淥verall, this research feels both alarming and motivating.鈥�